As part of our Math Awareness Month celebrations, we posed 7 Questions to Richard Alley, one of the world’s leading climate researchers, and he obliged us with a very thoughtful interview on the present and future of this important area of study. Alley, Professor of Geosciences at Pennsylvania State University, studies how glaciers affect climate, sea level, and landscapes. He has won both teaching and research awards for his work, which has included five expeditions to Greenland and three to Antarctica. He is also the author of The Two-Mile Time Machine: Ice Cores, Abrupt Climate Change, and Our Future.
PUP: What are you currently working on?
Richard Alley: Big Picture: will the ice sheets fall in the ocean and flood the coasts; and, what does the history of the Earth’s climate tell us about the near future. In more detail, we have just submitted or are about to submit several papers, on which I’m coauthor with students or postdocs or colleagues, that address: i) outburst floods rushing from one lake to another beneath an Antarctic ice stream; ii) why we need to know about the deformation of till (unconsolidated sediment) beneath the ice streams, to predict what the ice sheets will do; iii) when, after Europeans reached North America and transmitted diseases to the native peoples that caused huge die-off, what the resulting change in human activity did to the atmosphere; iv) the role of meltwater wedging open crevasses in determining the rate at which ice-sheets grow and shrink during ice ages; v) new ways to use the deposits left by glaciers to learn how large and rapid the climate changes were that caused the glaciers to leave those deposits.
PUP: How did you become interested in this field?
RA: I chose geology because of my interests in caving, hiking, rock collecting, and general out-of-doors-ing. I focused on ice initially because the glaciologist at Ohio State had a summer job. But, I stayed with ice because it is so important and interesting.
PUP: How do you use mathematics in your work?
RA: Anything we measure turns into a number, and we need to keep track of those numbers and work with them. Here is one example of many. Recently, we were interested in the question of how meltwater gets to the bed of a glacier. Water in Greenland flows down great holes, called moulins, huge funnels that plunge most of a mile to the bed of the glacier. But, nature lacks “drills” to make such holes. So, we worked up a physical model, considering what tools nature does have. Our result was that first a crack must open. Where the crack is thin, the cold ice will refreeze the water; where the crack is thicker, water flow will make enough “frictional” heat to keep the flow going, eventually making the hole. This model is done in equations, and we “ran the numbers”, finding that one needed a big reservoir of water to drive a crack all the way through the ice and along the bed to the ice front, and to make enough heat to keep a “pipe” open. So, we suggested that the moulins formed by crevasses opening under lakes that form in hollows on the surface of the ice sheet. A former student, Sarah Das, and a colleague, Ian Joughin, then were able to obtain funding to go look for this and see whether we “got it right”. They were next to a lake when the crack opened beneath it, causing water to fall into the ice sheet faster than Niagara Falls, raising the ice and causing it to lurch forward. Our mathematical work with the physics had successfully predicted what they observed.
PUP: How is mathematics helping us to understand climate change and how the earth works?
RA: We use math to track the data. We put the physics into math in the computers to help interpret the data, and to help predict the future. The computer models are now showing real skill in predictions—scientists a decade or two made projections based on mathematical representations about the physics of the climate, and on pretty good guesses about what humans would do, and those projections are proving to have been accurate—the specific humidity of the atmosphere is rising, the dry zones of sinking air where the tropical circulation comes down are expanding, and so on.
PUP: What are the top 3 biggest problems in climate science that still need to be solved? How will mathematics help solve these problems?
What will the ice sheets do? What will clouds do? And, what will people do? Mathematics is surely needed to solve the first two, and I suspect math will prove more important than ever in solving the third one.
RA: Why should students who are good in math consider research in climate or earth science? Climate and Earth science really matter. In climate science, humans are going to make decisions about our energy future whether to invest close to a trillion dollars per year to avoid future damages of many trillion dollars per year. Dollars are a way of measuring food and medicine and shelter and other things, so we’re talking about people’s lives. We must get the science right on this; too much depends on it for us to be sloppy.
PUP: What books, Princeton or otherwise, would you recommend to people who want to learn more about how mathematics and physics are helping us to understand how climate works?